1. Technical Field of the Invention
This invention relates to a hollow shaft member to be fitted to a member having holes therein, and more particularly this invention mainly relates to a shaft member to be fitted to members having holes therein for a bearing or a paper feed roller or a paper presser roller and the like for office machines such as a printer for computer, a copying machine, a word processor, a facsimile device or the like, and an ATM. (Auto Tellers Machine) used in a financial organization, computer-based devices and measuring units etc.
2. Related Art
In the prior art, although the shaft members for use in installing a ball bearing, a paper feed roller or a paper presser roller and the like, for example, are used in the aforesaid office machines or ATM, a computer, a measuring device and the like, it is a normal matter that as the shaft members, a solid member is used (refer to FIG. 11).
However, such a solid member causes its weight to be heavy. Moreover, in the case that a size of fitting to a bearing hole, etc. is larger than that of a theoretical value when the end part of the solid member is fitted to the bearing hole of the ball bearing, it must be required to attain a precision in size in a unit of micron due to preventing the disadvantages such as a fatigue life, vibration, noise and generated heat to be produced. In addition, in order to perform a smooth rotation of it, it is also required to provide high circularity as well as a degree of coaxial state.
Accordingly, the prior art had a disadvantage that a manufacturing process becomes quite complex and a product cost is increased.
In addition, in the case that a member such as a paper feed roller or a paper presser rotor or the like is installed at the shaft member, a fitting female thread must be punched at the paper feed roller and the shaft member, and then a male screw is threadably engaged with the female thread to connect them to each other, resulting in that a required accurate positioning for fitting female thread and male thread each other make a manufacturing process be complicated.
The present invention has been developed in order to eliminate the aforesaid disadvantages, wherein the shaft member is made as a hollow member to reduce its weight, it can be easily installed at a ball bearing or a paper feed roller and an appropriate force coupling can be attained between it and an objective member under application of a structure of the shaft member.
The hollow shaft member of the present invention relates to a hollow shaft member made of metallic material to be fitted to an objective member such as a bearing member having holes therein, wherein its circular sectional plane is divided into three or more outer arcs m1, m2, m3 . . . and three or more inverse directed inner arcs n1, n2, n3 . . . are formed among the outer arcs, the hollow member is inserted into the objective member with the outer arcs and the inner arcs being compressed inwardly and deformed, and when the objective member and the shaft member are coupled to each other by a resilient restitution force generated under the compression and deformation, the aforesaid outer arcs m1, m2, m3 . . . and inner arcs n1, n2, n3 . . . satisfy the following conditions (1) to (4); i.e.
(1) a relation of Rs greater than Rt should be kept, where
Rs: a radius of sectional circle of the shaft member before its installation
Rt: an inner radius of hole of an objective member to which the shaft member is fitted;
(2) a relation of (Lm1+Lm2+Lm3 . . . ) less than 2xcfx80Rt should be kept, where
Rs: a radius of circular sectional shape,
Rt: an inner radius of hole of an objective member to which the shaft member is fitted
Lmi: length of an outer arc mi (i=1,2,3 . . . )
(3) Radii of curvature xcfx81nsi, xcfx81msi of each of the arcs should be defined such that a resilient restitution force Ft generated between the shaft member and the inner wall surface of a hole of the objective member by bending moments Mni and Mmi described below, may become a value adapted for a coupling between the shaft member and the objective member.                               M          ni                =                              EA            ni                    ⁢                      κ            ni                    ⁢                                    ρ              nti              2                        ⁡                          (                                                1                                      ρ                    nsi                                                  -                                  1                                      ρ                    nti                                                              )                                                          Equation        ⁢                  xe2x80x83                ⁢                  (          1          )                    
xcfx81nsi: a radius of curvature of the axial line of the inner arc before its curved deformation
xcfx81nti: a radius of curvature of the axial line of the inner arc after its curved deformation fitted to an objective member
E: a longitudinal elasticity of the shaft member
Ani: a sectional area per a unit of length of the inner arc
xcexani: a sectional coefficient of the inner arc by a bending moment Mni (i=1,2,3 . . . ) generated at the inner arc when the shaft member is compressed and deformed                               M                      m            ⁢                          xe2x80x83                        ⁢            i                          =                              EA                          m              ⁢                              xe2x80x83                            ⁢              i                                ⁢                      κ                          m              ⁢                              xe2x80x83                            ⁢              i                                ⁢                                    ρ              mti              2                        ⁡                          (                                                1                                      ρ                    msi                                                  -                                  1                                      ρ                    mti                                                              )                                                          Equation        ⁢                  xe2x80x83                ⁢                  (          2          )                    
xcfx81msi: a radius of curvature of the axial line of the outer arc before its curved deformation
xcfx81mti: a radius of curvature of the axial line of the outer arc after its curved deformation fitted to an objective member
E: a longitudinal elasticity of the shaft member
Ami: a unit sectional area of the outer arc
xcexami: a sectional coefficient of the outer arc by a bending moment Mmi(i=1,2,3 . . . ) generated at the outer arc when the shaft member is compressed and deformed
(4) Extensions of the symmetrical lines C1, C2, C3. of the inner arcs n1, n2, n3 . . . should pass through a center O of a circle S and the symmetrical lines C1, C2, C3 . . . are crossed to each other at an equal angle. In reference to the aforesaid configurations, the present invention may provide the following superior effects.
(1) The present invention based on the aforesaid configuration is not only light in weight but also can be manufactured quite easily as compared with the prior art shaft member if a drawing work with female mold dies having outer arc and inner arc formed therein as well as the dies, it can be manufactured quite easily, so that its manufacturing step can be remarkably simplified.
(2) Proper setting of the radii of curvature of the outer arc and the inner arc enables a resilient restitution force required for coupling with the objective member to be attained and in the case of coupling with a ball bearing, for example, it is possible to set an inner clearance to a value not exceeding its theoretical value.
In addition, in the case of coupling with a paper feed roller and a paper presser roller and the like, it is possible to attain a high coupling state durable against it and an appropriate setting of radii of curvature of the outer arc and the inner arc in advance enables a proper setting to be carried out against an expected requite coupling force.
(3) Since high circularity can be sufficiently provided under arrangement of the symmetrical line of the inner arc toward the center point and an equal distribution arrangement, a smooth rotation of the shaft member is assured and an irregular rotation called as an improper action can be prevented.